Generic permanently excited synchronous machines are known from the prior art. They are commonly used for small to medium power requirements and can operate as generators for power generation and as synchronous motors. However, even higher outputs are increasingly being realised. For example, wind turbines are sometimes equipped with permanently excited synchronous machines. Permanently excited synchronous machines have a rotor, which has permanent magnets magnetised in the direction of the flux guide regions of the stator or in the opposite direction. If the winding of the stator generates a magnetic field, the poles of the permanent magnets are correspondingly drawn to the poles of the rotating field, so that opposing magnetic poles always face each other. The torque of the synchronous machine is thus generated in that the magnetic poles of a rotatably mounted, permanently excited rotor follow a magnetic rotating field generated in the stator.
From US 2010/019606 A1 an electric motor with a stator and a rotatably arranged rotor with axially spaced rotor cores is known, wherein rotor teeth and radially magnetised permanent magnets are alternately arranged on the rotor cores. The document US 2005/099082 A1 concerns an AC synchronous motor comprising a rotor with a plurality of circumferentially arranged permanent magnets as well as a stator with a plurality of stator poles.
The document DE 41 15 887 A1 reveals an electric machine with a stator and a rotor fitted with permanent magnets, wherein the magnetic flux can be changed with the aid of a control coil and thus an appropriate control or regulation can be carried out for different loads and/or operating speeds.
From document US 2010/176679 A1 an electric motor with a rotor, an exciter part and an armature, which has armature windings that are arranged circumferentially facing a rotor and serve to control the magnetic flux, is known.
The torque is usually dependent on the phase angle between the rotor and the magnetic rotating field, wherein the maximum value itself depends on the maximum magnetizability of the permanent magnets. When using, for example, neodymium permanent magnets, the maximum magnetic flux density in the usual temperature range for electric motors is up to 150° C. at approximately 1.4 T, which permanent magnets can provide. The provision of torques was previously limited with a constant overall size, due to the maximum flux densities provided by the permanent magnets.
However, there is a constant need to increase the achievable/usable torque of the synchronous machine in order to, for example, reduce the overall size, to reduce costs or to allow completely new applications on the basis of higher torques.
The present invention therefore has the object of providing a permanently excited synchronous machine with a flux concentration, which can provide improved characteristics with respect to the provision of torque, in a simple design.